Drupal页面中的全局PHP变量的范围是什么？

Question

Consider this PHP script:

<?php
  $a = "ok";
  function foo() {
    global $a; print "[$a]";
  }
  foo();
?>

It prints [ok] when run with a PHP interpreter as one would expect. But it prints just [] if run in a Drupal page. To make it work in Drupal I have to add another global specification before the variable declaration thus:

<?php
  global $a; // WHY IS THIS NEEDED IN DRUPAL?
  $a = "ok";
  function foo() {
    global $a; print "[$a]";
  }
  foo();
?>

Answer 1

Likely because Drupal includes the file inside a function:

function render() {
    include 'my_script.php';
}

That makes $a local to the function, not global .